Control circuit for cathode-ray oscilloscopes



ay P. W. CRIST CONTROL CIRCUIT FOR CATHODE-RAY OSCILLOSCOPES Filed Oct.27. 1948 2 SHEETS-Sl-IEET l ld Q seals/0A o a 390.4 70A lq u ' zavaar/on c la 395.4 70A INVENTOR ATTORNEY Pfl/UP VM GR/ST May 6 1952 w.cRlsT 2,595,228

CONTROL CIRCUIT FOR CATHODE-RAY OsCILLosCoPEs Filed oct. 27, 1948 2sl-IEETs-sl-IEET 2 INVENT'OR Pff/L /P l/V. R/ST Patented May 6, 1952STATES PATENT OFFICE CONTROLCIRCUIT FOR CATHODE-l-RAY SCIBLOSCO'PES`Philip; W; Crist; Hempstead, N. Y., assigner to The ySperryYCorporation, Great Neck, N. Y., a.

corporationofDelaware Application octoerei, wcaseriamo; 56,778:

'll'ii'sl inventionv relates; to` controlv circuits. for. cathode-rayOscilloscopes and particularlyV to.

sweepi-andr intensity voltage .generators for controlling ther electronbeamof a cathode-ray tube.

Numerous arrangements have been devised: for generating non-sinusoidaloscillations `adapted to causelthe electronbeam in a cathode-ray'tubetobe' deflected byY electrostatic` means across the screen ofithetube atsubstantially constantspeed. Conventional arrangements employ arelaxation oscillator or a. complex vacuumV tube circuit` to generatesii-deflection` potentiell whose magnitude changesfin a substantiallylinear;A manner with respectutatime.. However; the-maximum sweep speedfobtainable with conventionalsweep:A gener-- ator-s2 is usually limitedbythe stray. capacities lintroduced 1 by thee component! parts,v of thecircuit, andi-therefore such'oscillators:are-not satisfactory for; thefgeneration' of' sweep signals for oscilloscopes which veryhigh'electronbea'rn Asweep speedsl must be# attained.

Itis a-nfobject'of thefpresent-invention tolprozvide` any improvedmeans-'for generating an electrostatic field-5 adapted to .cause theelectronbeam of" a'- cathod'e-ray tube to sweep across1 the screen ofthe tube at'n substantially constantrspeed.

It` is an` additional object' of this-.invention-to provide a means forgenerating sweep voltage impulses adapted to causelthe electron beam ofa cathode-ray tube Vto'ai-.tain- Very high sweepspeeds.

It is affilrtlier object of this invention to provide an improved" meansfor generating intensity gate voltage impulsesadapted toA cause the:

electron beam-off a ca-thode-rayftubeto strikeathe screen of-Jthe tubeonly during the time intervals in which" sweep'- voltage* impulses areapplied tol the deflection pla-tes ofthe-tube.-

These and: other objectsof' the invention will be apparentfrom thefollowing'description, thea-ppendedcl'afims, and the drawings', inwhich,

Fig. 1': is a; diagram-of an oscilloscope, theicon-`trol*circuitfforfgenerating the-sweep `and intensity gate voltages; and?blockdiagrams of scorn/entional devices associated therewith;

Figs` 2; 3; -andi illustratemodifieationsL of the -sweepgen'eratorindi'cated-'infIFigt 1;-

Figa' 5"-*indicat`es-La-1 typical3 voltage-time curve for theVdeflection voltage f produced" by theV sweep l Fig. 8` indicates atypical voltage-time curve for the` intensity gate voltagevprod'uced bythe sweep generator disclosed infFig. 2. Y

The objectsY of this invention. are obtainedA by employing potentialsdeveloped` by a condenser discharge-current in an oscillatorycircuittocontrol the sweep and intensity of the electron beam of a cathode-raytube. The voltage variation across the condenserl` is employed as thesweep voltage, while a voltage developed across a re sistancel inthepath of the discharge current is` employed as an intensity gateimpulse. Special means are provided to insure that the discharge currentisboth rapid and substantially` constant and that the voltage variationacrossthe condenser changes in-a substantially linear: manner.

Fig. 1 shows anA embodiment of the. invention wherein. sweep generatorand oscilloscope 55 arel under the control of trigger generator. 52. Thetrigger generator serves to generate aseriesV of steep-wavefront:electrical impulses at apredeterminedfrequency such as 400 impulses persecond, and theseimpulses are applied directly to sweep generator 55 andvariabley delay network 53. The trigger impulses` ofvoltage developed`by trigger generator'52 areindicated adjacent to the connection` betweenthe' trigger generator and variableV delay network 53. Thel variabledelay.

network serves to introduce a controllable delay time between theimpulses introduced by generator 52fv andV those produced at: the outputofthe variable; delay network. 'Illel time relationship between` thetrigger. impulses'introduced by trigger generator 52and those producedatthe output y of variable delay network Eiifis:` indicated' on thedrawing,` the-.delayedfimpulsesbeingindicated adjacent vto.the-connection between variablev dela-y network:` i3.u and generator 54;Generator 5aY is actuated by the; delayedimpulsesi and serves togenerate the phenomenon-.whose wave formisto be observed on the:soreenof; cathode-ray tube` 57. The output'of generator.'tsis'connectedfacrosstheverticaldeflection plates. of cathode--raytube151 through condenser: 6b: and .potentiometer lt5 lin. a conventional.manner.

Sweep generator. 55 includes a grid-controlled gas. discharge tube 24which-isa'fast acting tube such as type'y 8845 manufactured; by the'.Radio Corporation off. America.. The gridV ofi this tube is.coupled totriggergenerator 52 through. acondenser'20. Tube 2li` isv normallybiased toA cut-or by battery 23 which. is connectedbetween' thecathode'. and. control 'grid' of the; tube throughfresistorsxZ-l; 22 and25. This bias is adjusted so; that .the tube. is caused to becomeconducting.

each time a trigger impulse is applied to the control grid throughcondenser 2U. The plate potential for the tube is supplied by battery 28through resistor 21, and these two circuit elements are connected acrossserially connected condenser 29 and inductance 38. The resistance ofresistor 21 is many times larger, by a ratio of 50 to 1 for example,than the surge impedance (i. e., \/L/C) of serially connected inductance30 and lcondenser 29. The sweep voltage for the horizontal deectionplates of cathode ray tube 51 is developed across condenser 29, and thisvoltage is designated by the symbol e1 in the drawings.

The intensity gate voltage which is applied to control electrode 58 ofthe cathode-ray tube through condenser 28 is developed as a voltage dropacross resistor 25 and is designated by the symbol e2 in the drawings.The resistance of resistor 25 is several times less than the surgeimpedance of inductance 38 and condenser 29, as by a ratio of l to 20for example; therefore, the closed circuit comprising inductance 3D,condenser 29, resistor 25, and the interelectrode space between theanode and cathode of tube 24 is oscillatory. The intensity gate voltageis applied between control electrode 58 and the cathode of tube 51 inopposite polarity to the negative bias applied between the controlelectrode and cathode by'potentiometer 68 through series resistor 69,and the circuit constants are proportioned so that the maximum value ofthe intensity gate voltage developed across resistor 25 partlycounteracts the negative bias and causes the intensity of the electronbeam of tube 51 to increase to substantially the maximum value allowablewithout damaging the screen of tube 51.

Oscilloscope 56 is a conventional type adapted to be employed in systemswherein the voltage applied between the horizontal deection plates isperiodically increased in a linear manner and then restored to normal,and the voltage applied between the vertical deection plates correspondsto the phenomenon Whose wave form is to be observed. The centeringvoltages for the vertical deection plates are provided by resistors 62,63 and 64 and potentiometer 65, al1 of which are connected to the powersupply and employed as a voltage divider. Resistor 6I serves to connectthe upper vertical deflection plate to the voltage divider and alsoserves to increase the resistance in the circuit interconnecting the twovertical deflection plates. No provision is made in this embodiment ofthe invention for applying centering voltages to the horizontal deectionplates;A however, horizontal centering may be provided in a conventionalmanner if it should be required in some systems in which this inventionmay be employed. Resistor 61 and potentiometers 68 and 68 are connectedto the power supply and comprise another voltage divider. The voltageapplied to focusing electrode 59 is supplied by potentiometer 66, andthe voltage applied to control electrode 58 is provided by potentiometer68 and connected to the control electrode through resistor 68.' The xedbias supplied by potentiometer 68 serves to make the control electrodeof negative polarity with respect to the cathode of tube 51 and this xedbias is sucient to cause control electrode 58 to extinguish the flow ofthe electron beam from th cathode to the screen of the tube.

Before the rst trigger impulse is generated,

gas tube 24 is in a non-conducting condition since it is biased tocut-off by battery 23. Neg- 4 lecting leakage currents, when the tube isin a non-conducting condition no current ows through resistors 25 and21, and voltage er across condenser 29 equals the voltage of battery 28,while the voltage drop e2 across resistor 25 is zero. Since the voltageacross condenser 29 is applied to the horizontal dellection plates ofthe cathoderay tube, it follows that an electron beam within tube 51would be deflected to the extreme left side of the screen. However,since the fixed bias Y applied to the control electrode by potentiometer88 is sufficient to'cut off the electron beam and since no intensitygate voltage appears across resistor 25 at this time to partlycounteract the iixed bias, there Ais no electron beam at this instantwhich can be aiected by the electrostatic eld caused by the voltageapplied to the horizontal deection plates. Thus, a spot does not appearon the screen of tube 51 at this time.

When the rst trigger impulse is generated by trigger generator 52 attime t1, the impulse serves to reduce or remove the bias between thegrid and cathode of gas tube 24 so that the tube becomes conducting.Because of the-charge stored in condenser 29, current ows from groundthrough condenser 29, inductance 3B, the interelectrode space betweenthe plate and cathode of tube 24, and resistor 25 to ground. Thecurrents owing in the branch of the networkcomprising battery 28,resistor 21, inductance 3B, and condenser 29 and in the branchcomprising battery 28, resistor 21, the interelectrode space between theplate and cathode of tube 24, and resistor 25 may be disregarded sincethe impedance of each of these branches is many times larger than theimpedance of the branch discussed above. When condenser 29 hascompletely discharged, the energy stored in inductance 38 serves tomaintain the flow of current in the condenser discharge path for a shortinterval of time and condenser 29 reverses its initial charge. When thevoltage across condenser 29 reaches its maximum negative value, themagnitude of the transient current through the discharge path is zero,andthe transient is interrupted since current ceases to flow throughtube 24 because the interelectrode space between the plate and cathodeof tube 24 is a unilateral conductor.

As soon as the transient current is interrupted, the condenser begins tocharge inan exponential manner, the charging circuit comprising condener29, inductance 38, resistor 21, and battery 28. The resistance ofresistor 21 is much larger than the surge impedance of inductance 3i)and condenser 29; therefore, the charging circuit is non-oscillatory.When condenser 28 is charged so that the voltage across the condensersubstantially equals and is the same polarity as the voltage of -battery28, the sweep generator is in condition to receive the next triggerimpulse which occurs at time t2. The sweep generator responds to thissecond impulse and the subsequent impulses in the same manner as itresponded to the first impulse. v

It will be observed that the time required to restore the charge incondenser 29 may be reduced somewhat by connecting serially connectedbattery 28 and resistor 21 directly across condenser 29. With such anarrangement, the circuit functions in substantially the manner asdescribed above.

As discussed above, the resistance of resistor resistor 25, theinterelectrode space between theA offered 4by the interelectrode` spaceVbetween the plate and cathode of tube 24 has a negligible effect uponthe wave form of the transient curerentI whichi'scaused to ow whencondenser 29A discharges and charges to a reverse voltage; therefore,the leffect of the circuit el'ementsother than condenser 29 andinductancea'in theidis-4 charge circuit may-'be disregarded forthepurposeV of" determining the-wave formV ofi' the discharge currentv andthe natural frequency ofi' the disl chargepath.v It* follows that-thehalf-cyclefcur-A rent-impulsey which flows is substantiallyy sinuf Thehalf-cycle voltage impulse CII age'is in-phase with the current, theintensity vIt'will be. observedV that the shunt effect of seriallyconnected battery 23 and resistor ZTupon the Wave form produced by andthe natural frequency of the discharge circuit has not been consideredin the foregoing discussion. This is justied since the combinedimpedance of these circuit elements is many times larger than theimpedance of the discharge'circuit which they are connected across. v

At time t1 which occurs slightly later than t1, variable delay network53 reproduces the impulse generated by'trigger generator 52. Thisdelayed impulse serves to` cause generator 54 to generate the electricphenomenon whose wave form isnto be observed on the screen ofcathoderay'tube 51'. The delay introduced by'networl;` 53 determines theinterval of time represented by 15V-tr, and adjustment of the delay isemployed to synchronize the signals generated by generators'54'and `55.Generator 55 must be actuated by-a.trigger. impulse ya short time beforegenerator 54 is: actuatedsincefafinite. time is required to`causeqthesweep generator to generate a sweep When.

, Fig. 5,-indicates atypical curve for the delico-- tion.; voltage, e1.developed across. condenser' 29. The portionlofthecurve from A to Balong the time axis. representsthe magnitude and polarity ofthezvoltagedeveloped across condenser 29 during fthe ,interval of time that tube 24is in aconducting condition. The portion of the curve from B` to, Crepresents' the magnitude and polarity of4 the voltage developed acrosscondenser 29 during thefinterval of timethattube 24 is in a.nonpconducting; condition-1 and while the; conf denser-'is rechargingto-its initial condition'.l The@ portion from C `to= D1' represents 1the .secondfiintereJ val of timethat tube.241isA in aiconductingfcondition.

Neglecting the eifect of the. resistance of the discharge pathcomprising condenser 29, inductance 30, the interelectrode spacebetweenthe plate and cathode of tube 24, and resistance 25, the naturalfrequency of the discharge path is represented as follows:

1. f 21rx/-L where f is the natural frequency in cycles per second, L isthe inductance of' inductance 3'0, and C is the capacitance of'condenser 29;` Inl Fig. 5 thewave form of thercurverindicatedfrom A toB4 and C to D- alongthe' time' axis maybe:l expressed" as'V e1=Ecosf=andthe wave form ofthe curvelfromBitoCfalongz ther timey axis isexpressed as where El isA the'. voltage across: battery; 2.8;., t. isitimeVRm is thezqresistance of;resistor 21,.and i is the base of natural.logarithmsa Fig- 6 indicates;` a. typical. curve: for theintensity'gate voltage e2 whichis developed. across. resistor 25.. Thefportion. of the` curve from A to:B.-.along theztime axis. representsthe; intensity; gate.l voltage. developed .whiletube 24. is inz a con-Aductingv condition; The portion; of the curve; from B to C represents.:the time: interval durf in. which tube. 24; ist in anon-conducting;cont-` dition, and again thel portion from C tot D rep@resents the voltage developed whenytube` 24 is conducting.` The.portionv of. the curve froml A to B and C to- D' may befrepresented as,follows:

ef: E'- 2Ee where R25 is thel resistance ofresi'stor 25; andthe othersymbols are as designated? above fior-the; discussioni of. Fig. 5. Thetime inter-val from` A to B and C to D along thetime; axisfor both`Figs. 5 and 6` equalsrone-half the naturalV period of theoscillatorycircuit, i; e'. 1r\/LC secondsi From an inspection of' thecurves in Fig. 5- it is' apparent thatl sweep voltage er which is-`applied between' thehorizontal d'e'ection plates of tubeA 51 is not oflinear waveform. However, the electron beam is caused to sweepacrosstheusable middle' section of the screen of thef cathode-ray tube in alsubstantially linear manner. Also, it is apparent" that the intensitygatevolt-v age is of sinusoidal wave form and therefore does-'not reachsui'cient magnitude t'o-sufciently reducethe xedbiassoas topermitthefelectron'y beam to pass through the tube andy strike" thescreen until a shortl interval ortimeafter lthe sweepJ voltageA isinitiated. When; the" magnitude of l thev intensity gate *voltage`decreases; theelecv tron beam is again kcut oi beforethe sweep volte agehas completed its swing; Thus, the elec'f tron beam does not strikev the'edgeof' each side of the'screen, and .it is not permitted to strikeanypart of the screen during theY time requiredforxthe sweep generatorvtov restore to normal'. Suitable values vfor the circuit constants.inthe' to:` sweep` the# electroni beam across thef screen 7 of a typeJP1 cathode-ray tube as manufacimpulse is substantially linear exceptduring a tured by Allen B. DuMont Laboratories at a rate very shortinterval of time at the beginning and of 8 inches per microsecond, areas follows: end of the impulse, and the wave form of the intensity gatevoltage impulse accordingly is substantially rectangular. It will beobserved' liglfarads that the intensity gate impulse is employed to R21560 0,00 ohms cause the electron beam of the cathode-ray tube R22 30 600Ohms to strike the screen of the tube only during the R25 110 ohmsintervals of time in which the sweep voltage R2s 100 000 ohms 10impulses change in a linear manner. the L30 417mmihenries electron beamis not permitted to strike the E23 45 Volts extreme edge of each side ofthescreen ofthe E28 300 volts cathode-ray tube nor 1s it permitted tostrike any part of the screen during the time required The resistance 0fCharging resistor 2 is gOV- 15 for the sweep generator to restore tonormal.

Czo 50 micromicroiarads crncd by the repeiticn rate at Which the SWeeDThe oscillatory circuit comprises inductance voltage is generated andthe capacitance to bey 3g and Condensers 2g and 39 in Fig 3 andinchargcd- If this resistance is 000 W, the curductances 40 and 4| andcondensers 29 and 42 rent Which this branch 0f the circuit causes t0 inFig. 4. It will be observed that inductance 40 flOW through tube 24 Whenthe tube 1S m a C011' 20 is electromagnetically coupled to inductance 4lducting condition Will Prevent the GU-he from in the embodiment of theinvention disclosed in extinguishing and becoming non-conducting Fig. 4.Each of these two embodiments illusafter a half-cycle 0f current haspassed through trate alternative means for attaining the same thedischarge path. If the resistance is too high, result as that; obtainedby the apparatus disthe Sweep Voltage Will be reduced if the SWeeD 25lclosed in Fig. 2. The operation of the apparatus voltage impulses arerepeated at 2 high ra'eembodiments disclosed in Figs. 2, 3 and 4 is theThe limits within which the resistance must same as that discussed abovein connection with fall may be determined experimentally by using Fig, 1

a variable resistance t0 determine When the Suitable values for thepulse-forming network phenomena described above occur. and condenser 29indicated in Fig. 2 adapted to A Sweep generator of this type is capableof generate a substantially linear sweep voltage of causing the electronbeam 0f a cathode-ray tube 2 microseconds duration are as follows: tosweep across the screen of the tube at a very high speed. Sweep speedsin excess of 30 inches per microsecond have been obtained, and at thesespeeds it is possible to examine wave fronts as short as .04 microsecondin duration with rea- Czg 220 niicromicrofarads C35 130 micromicrofaradsC36 140 micromicrofarads C37 160 micromicrofarads L31 390.5 miilihenriessonable accuracy. The maximum sweep speed obtainable is limited atpresent by the cathodenlillllses ray tubes available. 40

In various applications, it is desirable that L34 37 mlumemles theelectron beam sweep across the entire screen It will be apparent to oneskilled in the art of the cathode-ray tube at a constant speed. thatvarious arrangements may be employed in- This requires that a voltage beapplied between stead of the pulse-forming networks Shown. thehorizontal deflection plates which increases Also, it will be apparentthat various other arin a linear manner. The modifications of therangements may be employed for synchronizing sweep generator asindicated in Figs. 2, 3 and 4 the sweep voltage generator with thegenerator are capable of repeatedly producing voltage imof the wave formwhich is to be observed on the pulses of this type. Also, thesemodifications soreenof the cath0de1-ay tube,

of the sweep generator are capable of generating Although Specific@mbodin-mts4 of this invennten'sty gate Voltage impulses Which effe 0fSubj tion have been shown and described, it will be Stanplanyrecfanguiar Wave form- 'Ifhls result 1S apparent that variousmodications may be made attamed by msertmg a' pulse'formmg networktherein without departing from the scope therein series with thedischarge circuit for condenser 29. There are several well-known methodsfor .causing the wave form of the currentresulting from the discharge ofa condenser in an oscillatory circuit to attain a rectangular wave form,

and the networks indicated in Figs. 2, 3 and 4 are three of the betterknown methods' 60 nected in series with said capacitor, a high im- Itwiii be observed in Fig. 2 that influer-ames pedfm Cifuit for chargingSaid Capacitor an 3l 32 33 and 34 and condensers 2g 35' 3G andoscillatory circuit including said capacitor and 31 comprise theoscillatory elements ofthe dis- Sgtlw irpriedane Sadhseliauy connectedca' charge circuit and that this embodiment of the nceo van l mp8 ncegmg Surge imped" invention differs from that disclosed in Fig. 1 65 Seera lmes erger an t e resistance 0f the oscillatory circuit means forcausing said cah t d t n e 2,33 d34 and ondense gat 396 aidu beenaddedto (attain n' Paoli '00 dlschargc and recharge to a potential f oppositepolarity through said oscillatory cirdesired dischar e current waveform. The wave o forms of the svp voltage and discharge en cuit during atime interval` equal to `one-half the rent produced by 'the apparatus isindicated in 70 naturalperiod of said oscillatory circuit, inter- Figs 7and 8 respectively As before the mag- Come'mg means for applungt thevoltage dej ve ope across sai capaci or o a pair of the estaartiglieriaessere gf eine me or app ying a xe i ias e Ween e control the magnitudeof the half-cycles sweep vonage electrode and cathode of saidcathode-ray tube, impulse. The wave form of the sweep voltage 5 andinterconnecting means for applying the voitof as defined by the appendedclaims.v

What is claimed is:

1. In combination, a cathode-ray tube employing electrostatic elds forthe deflection of an electron beam, a capacitor, a low impedance conagedrop developed facross said "low impedance vwbetween the controlelectrode and cathode of ,.resistoryzaunilateral Ydischarge device; alnonoscillatory circuit for charging said capacitor; an oscillatorycircuit including said capacitor, inductor, resistor and dischargedevice, said capacitor and inductor being connected in series and havinga surge impedance several times larger than the resistance of theoscillatory circuit; means for causing said discharge device to benormally non-conducting; means for periodically causing conductionthrough said discharge device during time intervals equal to one-halfthe natural period of said oscillatory circuit; interconnecting meansbetween said capacitor and a pair of the deflection plates of thecathoderay tube of said oscilloscope for applying the voltage acrosssaid capacitor to the deflection plates; means for applying a xed biasbetween the control electrode and cathode of the cathode-ray tube ofsaid oscilloscope; and interconnecting means between said resistor andthe control electrode and cathode of the cathoderay tube of saidoscilloscope for applying the voltage drop developed across saidresistor between the control electrode and cathode in opposite polarityto said xed bias.

3. Oscilloscope apparatus for affording very rapid sweep speedscomprising a cathode-ray tube employing electrostatic fields for thedeflection of an electron beam, a source of Xed bias of suiiicientmagnitude to extinguish the electron beam of said cathode-ray tube; acapacitor; an inductor; a resistor; a grid-controlled gas dischargetube; a resonant circuit including said capacitor, inductor, resistor,and the interelec trode space between the anode and cathode ci saiddischarge tube, all serially connected; Said resonant circuit having asurge impedance several times larger than the resistance of saidresistor; a source of potential; a high impedance circuit connectingsaid capacitor across said source of potential, said source of potentialbeing of a polarity to cause the anode of the discharge tube to be ofpositive polarity with respect to the cathode; a source of bias forcausing said discharge tube to be normally in a nonconducting condition;means for recurrently initiating conduction through said discharge tube;interconnecting means for connecting said capacitor across a pair of thedeflection plates of said cathode-ray tube; and interconnecting meansfor applying the voltage impulse developed across said resistor betweenthe control electrode and cathode of said cathode-ray tube in oppositepolarity to said xed bias.

4. In combination, a cathode-ray oscilloscope having an electrostaticdeflection circuit and a `beam control electrode circuit, a capacitorand an inductor connected in series, a gaseous discharge deviceconnected to said serially connected capacitor and inductor, means forperiodically rendering said discharge device conductive for rapidlydischarging said capacitor through said inductor, said seriallyconnected capacitor and inductor having a surge impedance several timeslarger than the resistance of the discharge path for said condenser,means for recharging said capacitor recurrently following the successivedischarges thereof, means connecting `saidlcapacitor insaidoscilloscopedeflection circuit, an impedance connected in series with said gaseousdischarge device, and means connecting saidimpedance in saidoscilloscope beam control `electrode circuit for actuating the electronbeam of said cathode-ray oscilloscope only during the rapid dischargesof said capacitor.

5. The combination of claim 4, wherein said Vimpedance is a lowresistance.

6. In combination, a cathode-ray oscilloscope having an electrostaticdeflection circuit and a beam control circuit, a capacitor and aninductor and a wave-shaping network connected in series, a gaseousdischarge device connected to said serially connected capacitor andinductor and wave-shaping network, means for periodically rendering saiddischarge device conductive for rapidly discharging said capacitorthrough said inductor and wave-shaping network, means for rechargingsaid capacitor recurrently following the successive discharges thereof,means connecting said capacitor in said oscilloscope deflection circuit,an impedance connected in series with said gaseous discharge device, andmeans connecting said impedance in said oscilloscope beam controlelectrode circuit for actuating the electron beam of said cathode-rayosoilloscope only during the rapid discharges of said capacitor.

'7. Apparatus for generating rapid sweep voltage excursions atpredetermined time intervals and gate pulses substantially coextensivetherewith. comprising a gaseous discharge tube having a cathode and ananode, an inductor, a capacitor, and a low impedance connected in seriesbetween said cathode and anode, said inductor and capacitor having avery short oscillatory period, means normally biasing said tube tocut-01T, means for charging said capacitor, means for recurrentlyinitiating conduction through said tube at a recurrence period muchlonger than said oscillatory period for initiating discharges of saidcapacitor, and a pulse-forming network coupled to said capacitor forrendering the discharge rate of said capacitor substantially uniform,wherebv said rapid sweep voltage excursions are produced across saidcapacitor and said gate pulses are produced across said low, impedance.

8. A generator for generating an impulse of voltage of a magnitude whichchanges in a substantially linear manner with respect to time comprisinga capacitor; a grid-controlled gas discharge tube; a pulse-formingnetwork including said capacitor; a resonant circuit including saidpulse-forming network and the interelectrode space between the anode andcathode of said discharge tube, said resonant circuit being adapted tocause the capacitor discharge current to be of substantially rectangularwave form; means for causing said discharge tube to be normallynon-conducting; means for recurrently initiating conduction through saiddischarge tube; and means for recharging said capacitor recurrentlyfollowing the successive discharges thereof.

9. A generator for generating an impulse of electric current ofsubstantiallyrectangular wave form comprising a capacitor, a resistor, aunilateral discharge device, and a pulse-forming network including saidcapacitor, all serially connected in a closed oscillatory circuit; ahigh impedance circuit for charging said `capacitor; means for causingsaid discharge device to be l? l2 `normally non-conducting; and meansfor caus- REFERENCES CITED ing conduction through said discharge devicefor The following references 'are of record in the a time interval equalto one-half the natural fue of this patent: period of said resonantcircuit, thereby causing said capacitor to discharge and recharge to apo- 5 UNITED STATES PATENTS tential of opposite polarity to the initialpoten- Number Name Date tial, said oscillatory circuit being adapted tocause 2,294,015 Salb et al. Aug. 25, 1942 the Voltage appearing acrosssaid capacitor dur- 2,457,744 Sturm Dec.28, 1948 ing said time intervalto be of substantially linear Wave form. l0

PHILIP W. CRIST.

